Electric circuit breaker



P 1948- R. N. BUTTRVEY 2,439,126

ELECTR I C CIRCUI T BREAKER Filed July 12, 1945 2 Sheets-Sheet 1 April 6, 1948. BUTTREY 2,439,126

ELECTRI C C IRCUIT BREAKER Filed July 12, 1945 2 Sheets-Sheet 2 .JSZiZ? alibi/1 6 2] If A Patented Apr. 6, 1948 ELECTRIC CIRCUIT BREAKER Ronald Norton Buttrey, Openshaw, Manchester,

England,-assignor to Cooke & Ferguson Limited, Openshaw, Manchester, England, a British ompany Application July 12, 1945, Serial No. 604,556 In Great Britain July 15, 1944 Claims. 1

The invention relates to electric circuit-breakers, particularly the single-break type of circuitbreaker in which a moving contact rod engages permanently with a sliding contact and when required with a current interrupting contact. In such circuit breakers the circuit is made to pass round sharp bends, e. g. between the terminal connections and moving contact portions, with the result that undesirable electro-magnetic forces are set up which tend to impede the normal operation of the circuit-breaker contacts.

The object of the present invention is to pro vide simple and conveniently applied means for minimizing the disadvantageous efiects before indicated of the sharp bends in the circuit.

My invention comprises the incorporation of a magnetic screening constructed of magnetic material in one or more of the circuit breaker contact parts.

My invention further comprises the incorporation of a magnetic screening device made of magnetic material in one or both of the circuitbreaker contacts so that one or both ends of the sliding contact rod is or are magnetically screened.

The magnetic screen may be a complete ring or annulus or may be part of a ring or annulus. With the part annulus or semi-cylindrical screen, attractive forces exist between the screen and contact rod counterbalancing any net electromagnetic forces on the current carrying parts; with a complete annular screen, there is no counter-active force created, but the efiect is to tend to centralize the contact rod along the axis of the screen.

The screens may be incorporated in or connected to the contact parts in any suitable manner.

Referring to the accompanying explanatory drawings:

Figure 1 shows a single break type of circuit breaker with magnetic screening means constructed and arranged in one convenient form in accordance with this invention.

Figures 2 and 3 are sectional views on the line 2-2 of Figure 1 and shows the eiiect of the magnetic screening material arranged in two different ways in diverting the magnetic flux so that the net flux through the contact rod near its ends is small,

The moving contact rod a makes permanen sliding contact with the contact I) and is moved into and out of contact with the current interrupting contact 0.

The contact rod is normally acted upon by electro-magnetic forces in the direction indicated by the arrows X due to the flux from the current carrying portions, in particular the vertical connectors f and 5!, so that these forces are mainly concentrated at each end of the contact rod. To obviate this and to screen the current carrying contacts from magnetic fields so reducing the electro-magnetic forces on the contacts, screens d, e of magnetic material are provided, d being incorporated in the current interrupting contact 0 and e being incorporated in the sliding contact I Figure 2 shows a screen at constituting a complete cylinder around the contact 0. It will be seen that the magnetic flux is diverted from the end of the contact rod a; it has the effect of tending to centralize the contact rod along the axis of the screen.

In Figure 3 the screen :1 is of approximately semi-cylindrical form and the magnetic flux is diverted through it as shown; attractive forces exist between the screen and the contact rod. The unscreened portion of the latter is mainly the middle part where the forces are relatively small. They are counterbalanced by the attractive forces between the screens (1 and e and the end parts of the contact rod.

The magnetic screen e serves to screen a portion of the contact rod a from the vertical connector I, whilst the magnetic screen (1 serves to screen a portion of the contact rod a from the vertical connector 9!.

What I claim is:

1. In an electric circuit breaker, having a sliding contact rod and contacts coacting therewith,

the incorporation of a magnetic screen made of magnetic material in at least one of the contacts for magnetically screening the part of the contact rod coacting therewith.

2. In an electric circuit breaker having a sliding contact rod and contacts coacting therewith, the incorporation in at least one of the contacts of a semi-annular screen of magnetic material for magnetically screening the part of the contact red coacting with said contact.

3. In an electric circuit breaker having a sliding contact rod and contacts coacting therewith, the incorporation in at least one of the contacts of a semi-annular screen of magnetic material arranged substantially coaxially with the contact rod and between the parts of the contact touching the rod and the conductor carrying current thereto, for magnetically screening the part of the contact rod coacting with the said contact.

4. In an electric circuit breaker having a sliding contact rod and contacts coacting therewith, the incorporation in at least one of the contacts of an annular screen of magnetic material arranged substantially coaxially with the contact REFERENCES CITED rod, for magnetically screening the part of the The following references are of record in the contact rod coacting with the said contact. file Of this Patent! 5. In an electric circuit breaker, the combina- 5 tion of a slidable contact Izod, anumber of contact UNITED STATES PATENTS elements arranged around and in contact with Number Name Date the rod, a conductor for carrying current to the 964,536 MCLeWee y 1910 contact elements, and a screen of magnetic mate- 31,370,139 Cohen 1 rial between the conductor and the contact-tele- 1f} 1,715,166. Esfihholz e 1929 ments for magnetically screening the contact rod. 2,312,992 Hlckman et a1 1943 RONALD NORTON BUTTREY; 

